The present invention relates to networks, and more particularly to generation of data used for network operation.
In some networks, network nodes store data which they use for proper operation. One example is squelch tables used in SONET rings. See Bellcore Generic Requirements document GR-1230-CORE (Issue 4, December 1998) incorporated herein by reference. In SONET, data between adjacent nodes are transmitted in modules called STS's (synchronous transport signals). Each STS is transmitted on a link at regular time intervals (for example, 125 microseconds). If a failure occurs, an STS may have to be squelched to prevent misconnection. To accomplish squelching, a node in a SONET ring stores a squelch table. For each STS handled by the node, the squelch table specifies a node on which the STS is dropped, and a node on which the STS is added. If an STS contains sub-STS structures such as virtual tributaries (VT's), the squelch table specifies, for each VT handled by the node, a node on which the VT is dropped and a node on which the VT is added.
Manual generation of squelch tables is a cumbersome and error-prone task. Therefore, squelch tables have been generated automatically. A separate computer, (for example, a UNIX station) can be connected to a node. The node requests data from other nodes regarding the STS's added and dropped on the other nodes, and provides these data to the computer. The computer constructs a squelch table for each node on the ring. The computer sends the squelch tables to the node to which the computer is connected. This node distributes the squelch tables to the other nodes on the ring.
It is desirable to facilitate generation of data used for network operation, and make the data generation more robust.
When failure occurs in a SONET ring, traffic can be switched from a “working” channel to a “protection” channel (a redundant channel) and transmitted in the opposite direction on the ring. When a SONET node receives traffic on the protection channel, the node may have to determine the format of the traffic to process the traffic correctly. For example, the node may have to extract the payload and re-transmit the payload further down the ring. The position of the payload in the SONET frame is defined by the frame's overhead pointers. The pointers' position in the frame depends on the type of the STS (e.g., a SONET OC48 link can carry an STS of type STS-48C or four byte-interleaved STS's of type STS-12C; the pointers' position will be different in each of these cases). Therefore, the node has to know the STS type.
Determining the STS type on the protection channel must be done quickly to avoid data loss or corruption. Quickly determining the STS type is a burden on the node's circuitry.
It is desirable to provide techniques that would allow a network node to quickly and easily determine STS types on protection channels.